Promise SuperTrak EX8650 SAS RAID Controller Review. Page 10

We upgraded our testbed for RAID controllers: now it includes SAS drives. The first one to be tested on this new platform is going to be a new solution from Promise – an 8-port SAS/SATA RAID controller.

Web-Server, File-Server, Workstation Patterns

The controllers are tested under loads typical of servers and workstations.

The names of the patterns are self-explanatory. The request queue is limited to 32 requests in the Workstation pattern. Of course, Web-Server and File-Server are nothing but general names. The former pattern emulates the load of any server that is working with read requests only whereas the latter pattern emulates a server that has to perform a certain percent of writes.

It’s all well in File-Server: good scalability and predictable results (the RAID10 is slower than the same-size RAID0 due to the write requests present in this pattern).

Interestingly, the performance of the four-disk arrays depends less on the queue depth.

This group of arrays is not as good as the previous one. It is easy to explain why the eight-disk RAID6 is slower than the RAID5 if you recall the problems at writing due to the lack of the processor’s performance. As for reading, the array just has fewer free disks because it has to store two checksums.

The RAID0 and RAID10 deservedly take first places.

When there are no write requests, the controller’s ability to read from both disks of a mirror results in the RAID0 and RAID10 arrays having almost identical performance.

Once again we can note the dependence of performance on the queue depth with the four-disk arrays: they do not accelerate any further starting from a certain depth of the queue.

The RAID6 arrays are almost as fast as the RAID5 due to the lack of write requests.

The four-disk arrays again cease to accelerate from a certain queue depth.

The overall ratings look nice and pretty, showing that reading is about the number of disks rather than on the type of the array.